Methyl sulfone

Dimethyl sulfoxide, also known as dimethyl sulfoxide, is an important fine chemical raw material. It can be widely used in petroleum, chemical industry, medicine, electronics, synthetic fibers, plastics, printing and dyeing, pesticides, petroleum processing, organic synthesis and other industries, and can also be used as brake oil, antifreeze, metal paint remover, degreasing agent, capacitive medium, rare metal extractant and cosmetic additive. It is also called "universal solvent" because of its special solvent effect on chemical reactions and its solubility in many substances. Especially DMSO, because of its anti-inflammatory, analgesic, diuretic, sedative and wound healing effects, as well as its strong permeability to the body and its carrying and synergistic effect on other drugs, is also called "panacea" in the medical field.

As one of the few countries in the world that can produce DMSO, China is developing very rapidly. At present, the application research of dimethyl sulfoxide in China is mainly concentrated in the field of medicine. The most important and extensive use is as a reaction solvent for the synthesis of flexacillin, an intermediate used in drugs such as norfloxacin and fluazinic acid. In recent years, with the expansion of application scope and the rapid development of pesticide industry, the application of dimethyl sulfoxide in pesticide field has gradually attracted people's attention.

1 as the reaction solvent.

The boiling point of dimethyl sulfoxide is 189.0℃, which is suitable for high temperature reaction. It is reported in the literature that DMSO is used as the reaction solvent and the reaction temperature is 138~ 144℃, and the conversion rate and yield of condensation reaction are high. At the same time, the freezing point of 60% DMSO aqueous solution is only -80e, which can be used in some low-temperature reactions. Therefore, DMSO has dual functions of high-temperature solvent and low-temperature solvent.

In addition, DMSO can be used as a reaction solvent for the synthesis of diketene from acetic acid, which can greatly improve the conversion rate of the reaction. Diketene is an important intermediate for the synthesis of monocrotophos, pyrimidinphos, diazinon and other pesticides. In the process of preparing p-fluoronitrobenzene from p-chloronitrobenzene (an intermediate for preparing fluorine-containing herbicides), the reaction yield was increased from 50% to over 74% due to the use of DMSO. However, the rate of using DMSO as solvent in alkylation reaction is 105 times faster than that of using non-protonated solvent. For example, DMSO is used in the reaction of alkyl halides with inorganic cyanide to prepare alkyl nitriles and sodium nitrite to convert alkyl halides or α -halogenated esters into nitro compounds, which obviously improves the reaction rate.

Therefore, the significance of DMSO for chemical reaction is not only as a reaction solvent, but also as a new chemical reaction means and a new chemical preparation method, which has played a very good role in promoting the synthesis of pesticides.

Application of 2 in the synthesis of organofluorine compounds

The synthesis of fluorine-containing pesticides is a rapidly developing field of pesticides, so the preparation of fluorine-containing intermediates is particularly important. However, fluorination reaction is difficult and the conversion rate is not high, which affects the development of intermediate synthesis technology. DMSO can accelerate and catalyze some chemical reactions, which can significantly improve the conversion rate. For example, under normal conditions, aromatic fluoride can not be prepared by Swarts reaction, but after DMSO is used as the reaction medium, potassium fluoride and chlorinated aromatic hydrocarbons are more likely to undergo displacement reaction, and high yield of fluorinated aromatic hydrocarbons can be obtained.

3 as penetrant and synergist of pesticides.

Using the excellent permeability of dimethyl sulfoxide, dimethyl sulfoxide can also be used as a penetrant and synergist for pesticides. According to literature reports, dissolving fungicides in DMSO can effectively prevent fruit trees from rotting; Dissolving pesticides in DMSO can kill fruit-eating insects in trees and fruits.

Application of 4 in other organic synthesis reactions

DMSO is a strong polar aprotic dipole solvent, which can greatly accelerate the reaction speed in nucleophilic substitution reaction. This is mainly because DMSO can strongly solvate cations or positively charged groups, but can not well solvate anions, so these anions are very active in DMSO and become strong nucleophiles, which greatly accelerates the nucleophilic substitution reaction, so DMSO is very effective for nucleophilic substitution reaction.

In addition, DMSO is also widely used in electrophilic substitution, double bond rearrangement and ester condensation. Especially as an oxidant of primary alcohol and secondary alcohol commonly used in pesticide synthesis, the reaction effect is good. Therefore, DMSO is of great significance to pesticide synthesis.

5 Other uses in the field of pesticides

At the same time, DMSO has also played a very good role in other fields of pesticides. If 0.05% DMSO aqueous solution is directly sprayed at soybean flowering stage, the crop yield can be increased by10% ~15%; Dissolving formaldehyde vapor in DMSO can not only greatly reduce the irritation of formaldehyde, but also improve the fumigation and sterilization effect of formaldehyde. The development of these new uses is gradually broadening the application scope of DMSO in the field of pesticides.

As an important fine chemical product, dimethyl sulfoxide has many excellent characteristics. Domestic research institutions and production units should strengthen the research on its application fields, and constantly expand its application scope to better serve the pesticide industry.

Article from: China Pesticide Additives Network

Author: Zhang Haibin

Message 2:

Production technology and application of dimethyl Asiatic stone

ki.com.cn/Article/CJFDTotal-HGJJ702.0 12.htm

ki . com . cn/Article/cjfd 1997-gdhg 19970 1008 . htm

ki . com . cn/Article/cjfd 1999-syhg 1999 12054 . htm

Message 4:

Study on recovery of dimethyl sulfoxide

/detail.htm？ 493 137 (charge)

Message 5:

Dimethyl sulfoxide (DMSO) is a sulfur-containing organic compound with the molecular formula of (CH3)2SO. It is a colorless and transparent liquid at room temperature. It has the characteristics of high polarity, high boiling point, aprotic and easy to dissolve in water, and is known as "universal solvent"

Properties of 1 dimethyl sulfoxide

Dimethyl sulfoxide (DMSO) is a transparent, colorless, odorless (industrial products are slightly smelly due to other impurities), slightly bitter and hygroscopic flammable liquid. Very low toxicity and good thermal stability. Soluble in water, ethanol, acetone, ether, benzene and chloroform. It is a very inert solvent and can dissolve most organic and inorganic salts. Dimethyl sulfoxide without water is not corrosive to metals, but dimethyl sulfoxide with water is corrosive to metals such as iron and copper when heated, and is not corrosive to aluminum.

Physical characteristics are as follows:

Melting point,℃ 18.55

Boiling point,℃, 760mmhg (101.3kpa)189.0.

Density, g/cm3, D2041.1014.

The refractive index is 1.4783 at 20℃

Flash point (opening),℃ 95

Autoignition temperature (in air), 300-302℃

Volume expansion coefficient, cm3/℃

Steam pressure, 40℃, mmHg 1.6( 12.0kPa).

Specific heat, 13.5℃, kJ/mol 1.88.

Combustion heat, 25℃, kJ/mol 1978.6.

Heat of fusion, 65438 08.4℃, kJ/mol 6.53.

Explosion limit in air,% (by volume)

Lower limit 3-3.5

Upper limit 42-63

Two uses

Dimethyl sulfoxide is a widely used organic solvent and a very active reaction reagent, which is widely used in organic synthesis, medicine, veterinary drugs and pesticides.

Dimethyl sulfoxide is widely used as a solvent in organic synthesis and drug synthesis. For example, the synthesis of new quinolones, such as norfloxacin, fluazinic acid and their intermediates, the synthesis of levamisole, inositol nicotinate and berberine, the synthesis of albendazole by carbendazim, the synthesis of antioxidants 10 10, 1076, the synthesis of sucrose fatty acid esters, and the synthesis of p-nitrofluorobenzene and methyl ketone derivatives from p-nitrochlorobenzene.

As a selective solvent, dimethyl sulfoxide can be used to separate mixtures. For example, selective extraction of metal compounds, selective removal of acid gases, selective extraction of dienes such as acetylene, butadiene and isoprene, benzene, toluene, xylene, polycyclic aromatic hydrocarbons and heterocyclic compounds, selective removal of sulfides in petroleum, separation of impurities and by-products in dimethyl terephthalate, etc.

Dimethyl sulfoxide can be used as a solvent for the synthesis and spinning of many polymers. For example, it can be used as a solvent for the polymerization of acrylonitrile with other monomers, the synthesis of polyurethane, and the synthesis of polyimide and polysulfone resin. In recent years, Japan has studied the use of dimethyl sulfoxide as a solvent for polyvinyl alcohol spinning to improve the properties of polyvinyl alcohol fibers. At the same time, some people used dimethyl sulfoxide as solvent to study the esterification, etherification and acetalization of polyvinyl alcohol to prepare useful compounds. Dimethyl sulfoxide can also be used as anionic polymerization solvent of epoxy compounds, polyamide spinning solvent and so on.

Dimethyl sulfoxide has anti-inflammatory, analgesic, diuretic, sedative and other functions. It has been hailed as a panacea abroad and can be used as the active ingredient of some anti-inflammatory and analgesic drugs. In addition, dimethyl sulfoxide has excellent permeability and can be used as a carrier for some drugs, cosmetic additives and pesticide additives to improve its use effect. Animal experiments show that dimethyl sulfoxide can inhibit the development of tumor and treat myasthenia gravis.

Dimethyl sulfoxide, as the raw material of organic synthesis, can be used to synthesize fenthion pesticide, bis (trichloromethyl) sulfone, dimethyl sulfone and so on.

Dimethyl sulfoxide has many other uses, for example, it can be used as synthetic fiber dyeing solvent, dye remover, dye carrier, synthetic fiber modifier, antifreeze, paint remover, preparation of non-toxic autoradiography imaging accelerator, ultraviolet spectrum analysis reagent and machine degreasing agent for polycyclic and polycyclic aromatic hydrocarbons such as food wax and edible white oil, etc.

Production method of 3 dimethyl sulfoxide

There are many ways to produce dimethyl sulfoxide, but dimethyl sulfide oxidation is widely used at home and abroad. Because the oxidant and oxidation method used are different, the production process is also different:

3. 1 nitric acid oxidation method

Dimethyl sulfoxide can be prepared by oxidizing dimethyl sulfide with nitric acid with a relative density of 1.34- 1.36. The reaction formula is as follows

3(CH3)2S+5 HNO 3→3(CH3)2SO HNO 3+2NO+H2O

Crude dimethyl sulfoxide contains a lot of nitric acid, which can be neutralized by CaCO3 or Na2CO3. The yield is 80%. During the reaction, beware of excessive dimethyl sulfide, otherwise it will explode. The equipment of this method is seriously corroded and the reaction conditions are difficult to control. Neutralizing nitric acid will consume a lot of soda ash and generate a lot of nitrate, so the refining process is inefficient. Therefore, it is difficult to be used in large-scale industrial production.

3.2 Peroxide oxidation method

(1) dimethyl sulfoxide can be prepared by oxidizing dimethyl sulfide with 35-55 wt% hydrogen peroxide in a dilute solution of dimethyl sulfoxide. The reaction temperature was 30-40℃, and the molar ratio of methyl sulfide to hydrogen peroxide was 1.05- 1.25, and the reaction was carried out in a multistage series reactor. Dimethyl sulfide in crude dimethyl sulfoxide was removed by extraction, and finally dehydrated by reduced pressure distillation or boiling distillation (boiling matter is benzene) to obtain high purity dimethyl sulfoxide.

(2) Using acetone as buffer medium, dimethyl sulfide reacts with hydrogen peroxide. Without neutralization, high-purity finished products can be obtained by direct distillation, and acetone can be recycled. This method can realize continuous production.

Besides hydrogen peroxide, alkyl peroxides, aralkyl peroxides and cycloalkyl peroxides can also be used as oxidants.

This method has high cost and large oxidant consumption, and is not suitable for large-scale industrial production.

3.3 Ozone oxidation method

The reaction formula of dimethyl sulfoxide generated by ozone and dimethyl sulfide is

(CH3)2S+O3→(CH3)2SO+O2

Firstly, oxygen and air are ozonated, and then dimethyl sulfide is oxidized to dimethyl sulfoxide and dimethyl sulfone at 30-40℃ with ozone as oxidant. The conversion of dimethyl sulfide is 26-28%, and the yield of dimethyl sulfoxide is 90%.

Ozone as oxidant is cheap, and the product purification is relatively simple. However, due to the low conversion rate of dimethyl sulfide, a large amount of dimethyl sulfide needs to be recovered.

3.4 Anodic oxidation method

In conventional or diaphragm-free electrolyzers, dimethyl sulfoxide is obtained by anodic oxidation of dimethyl sulfide.

(CH3)2S+H2O-2e→(CH3)2SO+2H+

The solvent used is dimethyl sulfoxide, and the electrolyte is halide, sulfate, nitrate and sulfonate of alkali metal and alkaline earth metal. The anode is graphite or platinum, and the cathode is platinum or stainless steel. By this method, dimethyl sulfide can be completely converted into dimethyl sulfoxide. After the reaction, dimethyl sulfoxide can be separated by extraction, rectification or crystallization.

This method has the advantages of economy, feasibility, safety and easy separation.

3.5 solid catalyst catalytic oxidation method

In the temperature range of 100-200℃, dimethyl sulfide was selectively oxidized by oxygen with V2O5 or Cr2O3 as catalyst, and dimethyl sulfoxide was mainly produced, and dimethyl sulfone was the by-product. Besides V2O5 or Cr2O3, Cu(VO3)2 can also be used as a catalyst.

3.6 Nitrogen dioxide oxidation method

Continuous oxidation of dimethyl sulfide by nitrogen dioxide oxidant to produce dimethyl sulfoxide is the most commonly used production method in industry, and the reaction formula is:

(CH3)2S+NO2→(CH3)2SO+NO

The generated nitric oxide reacts with oxygen to generate nitrogen dioxide, which can be reused. Nitrogen dioxide acts as a catalyst.

NO+ 1/2 O2→NO2+ 123.4 kj

The oxidation reaction can be carried out in liquid phase or gas phase. In the gas phase, it needs to be strictly controlled to avoid explosion. At present, liquid phase oxidation is widely used in industrial production devices.

There are two kinds of process flows, including single oxidation tower and multi-oxidation tower, as well as partial circulating dimethyl sulfoxide and non-circulating dimethyl sulfoxide.

The cocurrent tower liquid phase oxidation process is more advanced than the improved process of Toyo Rayon Company of Japan. The advantage of this improved method is to reduce the amount of NO2 catalyst and improve the conversion rate. Before improvement, the amount of NO2 was 4.95% (mol) of the raw material, and the conversion rate was 92%. After improvement, the NO2 content decreased to 3.07% (mol) and the conversion rate reached 96%.

Countercurrent tower liquid phase oxidation process is also a common process in industry, which is relatively safe, with high yield of dimethyl sulfoxide and full utilization of catalyst.

In some multi-tower processes, there are as many as four reactors. The first reactor is the main reactor, in which most dimethyl sulfide is oxidized into dimethyl sulfoxide by NO2, and unreacted dimethyl sulfide is blown out by N2 into the second reactor, where excessive NO2 is introduced to completely convert dimethyl sulfide into dimethyl sulfoxide, the third reactor is a NO2 regeneration reactor, and the fourth reactor is an absorption reactor, where NO2 is absorbed and recovered by dimethyl sulfoxide. The oxidation and regeneration of this process are carried out in different reactors, and the operation is relatively safe. Most NO2 is recycled, so the consumption of NO2 catalyst is low, and the content of nitrogen oxides in the discharged waste gas is low (0.3%), which is beneficial to environmental protection. However, this method has high cost and troublesome production control. Therefore, at present, the single tower process is mostly used in industrial production, and the oxidation reaction of dimethyl sulfide and the regeneration reaction of NO2 are completed in the same reaction tower. In order to reduce the amount of NO2 and its impact on the environment, a scrubber can be installed at the top of the reaction tower to recover part of NO2 absorbed and discharged by dimethyl sulfoxide, but this will correspondingly reduce the production capacity of the reaction tower and increase the investment and operating expenses. Because the waste gas discharged without scrubber can meet the national emission standard of three wastes, at present, the single-tower liquid phase oxidation process without scrubber is mainly adopted in China.

[This post was last edited by brucehan on 2008-12-2512: 01]

From:/spcpsppc/Chinese/TEP/2000 _ 06/3.html.